The invention relates to a positioning device having a guiding surface extending parallel to an X-direction and parallel to a Y-direction, a first object holder and a second object holder which are each guided over the guiding surface and are each displaceable parallel to the X-direction and parallel to the Y-direction from a first position into a second position, and a displacement system for displacing the first object holder and the second object holder over the guiding surface.
The invention further relates to a lithographic device provided with a radiation source, a mask holder, a focusing unit having a main axis, a characterization unit, and a positioning device, said positioning device comprising a guiding surface extending parallel to an X-direction, which is perpendicular to the main axis, and parallel to a Y-direction, which is perpendicular to the X-direction and the main axis, a first substrate holder and a second substrate holder which are each guided over the guiding surface and are each displaceable parallel to the X-direction and parallel to the Y-direction from a first position into a second position which is present near the focusing unit, and a displacement system for displacing the first substrate holder and the second substrate holder over the guiding surface.
A positioning device and a lithographic device of the kinds mentioned in the opening paragraphs are known from EP-A-0 687 957. The known lithographic device is used for the exposure of semiconductor substrates in the manufacturing process of integrated semiconductor circuits and operates according to the so-called step-and-repeat process. The known positioning device is used in the known lithographic device for displacing semiconductor substrates relative to the focusing unit and relative to the characterization unit. The first position of the known positioning device is a load and unload position in which a semiconductor substrate can be loaded on or unloaded from the first or the second object holder. The second position of the positioning device is an exposure position in which a semiconductor substrate present on the first or the second object holder can be exposed via the focusing unit. The first and the second object holder are displaceable from the first position to the second position and vice versa by the displacement system of the positioning device which is not described in detail in EP-A-0 687 957. When the first object holder is in the second position and the semiconductor substrate present thereon is being exposed, the second object holder is in the first position and a next semiconductor substrate is loaded thereon at first. Then the second object holder is displaced from the first position to a characterization position in which the semiconductor substrate present on the second object holder is characterized by the characterization unit. When the second object holder is in the characterization position, the first object holder and the second object holder are displaced lockstep-wise. In this manner the exposure of the semiconductor substrate present on the first object holder and the characterization of the semiconductor substrate present on the second object holder are carried out simultaneously, so that a high throughput of the step-and-repeat apparatus is obtained.
A disadvantage of the known positioning device and the known lithographic device is that the characterization of the semiconductor substrate present on the second object holder and the exposure of the semiconductor substrate present on the first object holder cannot be carried out independently from each other as a result of said lockstep-wise displacements of the first and the second object holder. As a result, the exposure of the semiconductor substrate present on the first object holder cannot be started until the second object holder has reached the characterization position.